Process for the preparation of ethylene copolymers

ABSTRACT

A polymerization process comprising contacting under polymerization conditions ethylene and at least one alpha olefin of formula CH2=CHA wherein A is a C 2 -C 20  alkyl radical to obtain a copolymer containing from 95% by mol to 50% by mol of ethylene derived units in the presence of a catalyst system obtainable by contacting:
         b) at least a metallocene compound of formula (I)       

     
       
         
         
             
             
         
       
         
         
           
             b) alumoxane or a compound capable of forming an alkyl metallocene cation; and optionally 
             c) an organo aluminum compound; 
             wherein the groups R 1 -R 4 , L, M and W are described in the text.

The present invention relates to a process for the preparation of ethylene/alpha olefins copolymers wherein the process is carried out in the presence of a metallocene based catalyst system having a particular substitution pattern.

WO 03/050131 describes a class of bridged bis indenyl metallocene compounds wherein the indenyl moieties are substituted at least in positions 2, 4 and 5. In this document about 100 pages are used to list example of compounds included in the general formula, al these compounds are bridged bis indenyl metallocene compounds substituted in positions 2, 4 and 5. WO 03/050131 states that this class of metallocene compounds can be used for every kind of polymerization process including solution polymerizations, however all the examples are directed to slurry polymerization process.

PCT/EP2004/013827 a class of bis indenyl metallocene compounds wherein the indenyl moieties are substituted in position 5 and 6 by a condensed ring is disclosed. PCT/EP2004/013827 is mainly focused on C₁ symmetric structures and there are no explicit disclosures of C₂ symmetric compounds. In other words this document is focused on metallocene compounds comprising two cyclopentadienyl moieties having different substitution patterns.

EP 05103955.0 relates to a solution polymerization process for the preparation of propylene/ethylene copolymers. This document is silent about the preparation of ethylene higher alpha olefins copolymers.

The applicant found that by using a metallocene-based catalyst system wherein the metallocene compound has a particular substitution patter it is possible to obtain ethylene based copolymers in high yields wherein the copolymers are endowed with a very high molecular weight.

An object of the present invention is a polymerization process comprising contacting under polymerization conditions ethylene and at least one alpha olefin of formula CH₂=CHA wherein A is a C₂-C₂₀ alkyl radical to obtain a copolymer containing from 95% by mol to 60% by mol of ethylene derived units in the presence of a catalyst system obtainable by contacting:

-   -   a) at least a metallocene compound of formula (I)

-   -   b) an alumoxane or a compound capable of forming an alkyl         metallocene cation; and optionally     -   c) an organo aluminum compound;     -   wherein in the metallocene compound of formula (I):         -   M is an atom of a transition metal selected from those             belonging to group 3, 4, or to the lanthanide or actinide             groups in the Periodic Table of the Elements; preferably M             is zirconium, titanium or hafnium;         -   X, equal to or different from each other, is a hydrogen             atom, a halogen atom, a R, OR, OR′O, OSO₂CF₃, OCOR, SR, NR₂             or PR₂ group wherein R is a linear or branched, cyclic or             acyclic, C₁-C₄₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀ alkynyl,             C₆-C₄₀-aryl, C₇-C₄₀-alkylaryl or C₇-C₄₀-arylalkyl radical;             optionally containing heteroatoms belonging to groups 13-17             of the Periodic Table of the Elements; and R′ is a             C₁-C₂₀-alkylidene, C₆-C₂₀-arylidene, C₇-C₂₀-alkylarylidene,             or C₇-C₂₀-arylalkylidene radical; preferably X is a hydrogen             atom, a halogen atom, a OR′O or R group; more preferably X             is chlorine or a methyl radical; L is a divalent bridging             group selected from C₁-C₂₀ alkylidene, C₃-C₂₀             cycloalkylidene, C₆-C₂₀ arylidene, C₇-C₂₀ alkylarylidene, or             a C₇-C₂₀ arylalkylidene radicals, optionally containing             heteroatoms belonging to groups 13-17 of the Periodic Table             of the Elements, or it is a silylidene radical containing up             to 5 silicon atoms; preferably L is Si(R₁₁)₂ wherein R₁₁ is             a linear or branched, cyclic or acyclic, C₁-C₄₀-alkyl,             C₂-C₄₀ alkenyl, C₂-C₄₀ alkynyl, C₆-C₄₀-aryl,             C₇-C₄₀-alkylaryl or C₇-C₄₀-arylalkyl radical; more             preferably L is Si(CH₃)₂ or SiPh₂;         -   R₁ is a linear C₁-C₄₀ hydrocarbon radical optionally             containing heteroatoms belonging to groups 13-17 of the             Periodic Table of the Elements such as methyl or ethyl             radical or an alpha branched aryl or arylalkyl radical             containing from 2 to 20 carbon atoms optionally containing             O, N, S, P and Se atoms, in particular O, N and S atoms such             as 2(5-Me-thiophenyl) or 2(5-Me-furanyl) radicals;             preferably R₁ is a linear C₁-C₂₀-alkyl, C₂-C₄₀ alkenyl,             C₂-C₄₀ alkynyl radical, optionally containing heteroatoms             belonging to groups 13-17 of the Periodic Table of the             Elements; preferably R₁ is a linear C₁-C₁₀-alkyl radical;             more preferably R₁ is a methyl, or ethyl radical;         -   R₂ and R₃, equal to or different from each other, are C₁-C₄₀             hydrocarbon radicals optionally containing heteroatoms             belonging to groups 13-17 of the Periodic Table of the             Elements or R₂ and R₃, are part of 4-7 membered ring             condensed to the benzene ring of the indenyl moiety said             ring optionally containing heteroatoms belonging to groups             13-17 of the Periodic Table of the Elements; the valence of             each atom forming said ring being substituted with R₁₈             radicals; that means that it is filled with R₁₈ groups,             wherein R₁₈, equal to or different from each other, are             hydrogen atoms or a C₁-C₂₀ hydrocarbon radical; preferably             R₁₈ is a hydrogen atom or a linear or branched, cyclic or             acyclic, C₁-C₂₀-alkyl, C₂-C₂₀ alkenyl, C₂-C₂₀ alkynyl,             C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or C₇-C₂₀-arylalkyl radical,             optionally containing one or more heteroatoms belonging to             groups 13-17 of the Periodic Table of the Elements; more             preferably R₁₈ is a hydrogen atom or a linear or branched,             C₁-C₂₀-alkyl radical; more preferably R₁₈ is a hydrogen atom             or a methyl or ethyl radical; said ring can be saturated or             it can contain double bonds; preferably R₂ and R₃, equal to             or different from each other, are linear or branched, cyclic             or acyclic, C₁-C₄₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀ alkynyl,             C₆-C₄₀-aryl, C₇-C₄₀-alkylaryl or C₇-C₄₀-arylalkyl radical             optionally containing heteroatoms belonging to groups 13-17             of the Periodic Table of the Elements or R₂ and R₃ are part             of a 5 or 6 membered ring; said ring optionally containing             heteroatoms belonging to groups 13-16 of the Periodic Table             of the Elements preferably groups 15-16 of the Periodic             Table of the Elements; the valence of each atom forming said             ring being substituted with R¹⁸ radicals; as described             above; preferably R² and R³, are C₁-C₂₀ alkyl radicals or             form together a condensed saturated 3-7 membered ring;         -   R⁴ is a hydrogen atom or a C₁-C₄₀ hydrocarbon radical             optionally containing heteroatoms belonging to groups 13-17             of the Periodic Table of the Elements; preferably R⁴ is a             hydrogen atom or a linear or branched, cyclic or acyclic,             C₁-C₄₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀ alkynyl, C₆-C₄₀-aryl,             C₇-C₄₀-alkylaryl or C₇-C₄₀-arylalkyl radical optionally             containing heteroatoms belonging to groups 13-17 of the             Periodic Table of the Elements; preferably R⁴ is a hydrogen             atom a C₁-C₁₀-alkyl or a C₆-C₄₀-aryl radical;         -   W is an aromatic 5 or 6 membered ring that can contain             heteroatoms belonging to groups 15-16 of the Periodic Table             of the Elements; the valence of each atom of said ring is             substituted with hydrogen atom or it can optionally be             substituted with R⁵ groups, wherein R⁵, equal to or             different from each other, are C₁-C₄₀ hydrocarbon radicals             optionally containing heteroatoms belonging to groups 13-17             of the Periodic Table of the Elements; preferably R⁵, are             linear or branched, cyclic or acyclic, C₁-C₄₀-alkyl, C₂-C₄₀             alkenyl, C₂-C₄₀ alkynyl, C₆-C₄₀-aryl, C₇-C₄₀-alkylaryl or             C₇-C₄₀-arylalkyl radicals optionally containing heteroatoms             belonging to groups 13-17 of the Periodic Table of the             Elements;         -   Preferably W is selected from the group comprising the             following moieties of formula (Wa), (Wb) and (Wc):

-   -   -   wherein the * represents the point in which the moiety             bounds the indenyl moiety of the compound of formula (I);         -   R⁶, R⁷, R⁸, R⁹ and R¹⁰, equal to or different from each             other, are hydrogen atoms or C₁-C₄₀ hydrocarbon radicals             optionally containing heteroatoms belonging to groups 13-17             of the Periodic Table of the Elements; preferably R⁶, R⁷,             R⁸, R⁹ and R¹⁰, are hydrogen atoms or linear or branched,             cyclic or acyclic, C₁-C₄₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀             alkynyl, C₆-C₄₀-aryl, C₇-C₄₀-alkylaryl or C₇-C₄₀-arylalkyl             radicals optionally containing heteroatoms belonging to             groups 13-17 of the Periodic Table of the Elements;         -   Z¹ is a nitrogen atom or a CR¹⁰ group; Z² is a nitrogen atom             or a CR⁶ group; Z³ is a nitrogen atom or a CR⁷ group; Z⁴ is             a nitrogen atom or a CR⁸ group; Z⁵ is a nitrogen atom or a             CR⁹ group; provided that not more that 2 groups among Z¹,             Z², Z³, Z⁴ and Z⁵ are nitrogen atoms, preferably not more             that one group among Z¹, Z², Z³, Z⁴ and Z⁵ is a nitrogen             atom;         -   Z⁶ is an oxygen atom, a sulfur atom, a NR¹³ group or a CR¹³             group; Z⁷ is an oxygen atom, a sulfur atom, a NR¹⁴ group or             a CR¹⁴ group; Z⁸ is an oxygen atom, a sulfur atom, a NR¹⁵             group or a CR¹⁵ group; Z⁹ is an oxygen atom, a sulfur atom,             a NR¹⁶ group or a CR¹⁶ group;         -   Z¹⁰ is a nitrogen atom or a carbon atom that bonds the             indenyl moiety of the structure of formula (I); with the             proviso that not more than 1 group among Z⁶, Z⁷, Z⁸, Z⁹ or             Z¹⁰ is a sulfur atom, an oxygen atom or a             nitrogen-containing group atom selected from NR¹³, NR¹⁴,             NR¹⁵, NR¹⁶, and a nitrogen atom;         -   R¹³, R¹⁴, R¹⁵ and R¹⁶, equal to or different from each             other, are hydrogen atoms or C₁-C₄₀ hydrocarbon radicals             optionally containing heteroatoms belonging to groups 13-17             of the Periodic Table of the Elements; preferably R⁶, R⁷,             R⁸, R⁹ and R¹⁰, are hydrogen atoms or linear or branched,             cyclic or acyclic, C₁-C₄₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀             alkynyl, C₆-C₄₀-aryl, C₇-C₄₀-alkylaryl or C₇-C₄₀-arylalkyl             radicals optionally containing heteroatoms belonging to             groups 13-17 of the Periodic Table of the Elements; more             preferably R⁶, R⁷, R⁸, R⁹ and R¹⁰ are hydrogen atoms,             C₁-C₄₀-alkyl or C₆-C₄₀-aryl radicals;         -   In the moiety of formula (Wa), in a preferred embodiment, R⁷             is a C₁-C₄₀-alkyl radical, preferably a branched             C₁-C₄₀-alkyl radical such as a tertbutyl radical, more             preferably R⁷ is a branched C₁-C₄₀-alkyl radical wherein the             carbon atom in position alpha is a tertiary carbon atom and             R⁶, R⁸, R⁹ and R¹⁰ are hydrogen atoms;         -   in a further preferred embodiment R¹⁰ and R⁸ are             C₁-C₄₀-alkyl radicals, preferably they are linear C₁-C₄₀             alkyl radicals such as methyl radicals and R⁷ and R⁹ are             hydrogen radicals;         -   in a further preferred embodiment R⁶, R⁷ and R⁸ are linear             or branched C₁-C₄₀-alkyl radicals such as methyl or             tertbutyl radicals and R¹⁰ and R⁹ are hydrogen atoms;         -   in a further preferred embodiment R⁶, R⁷, R⁸, R⁹ and R¹⁰ are             hydrogen atoms;         -   in the moiety of formula (Wb), in a preferred embodiment, Z¹             is a nitrogen atom and Z², Z³, Z⁴ and Z⁵ are respectively             CR⁶, CR⁷, CR⁸ and CR⁹ wherein the meaning of R⁶, R⁷, R⁸, and             R⁹ is described above; in a further preferred embodiment Z³             is a nitrogen atom and Z¹, Z², Z⁴ and Z⁵ are respectively             CR¹⁰, CR⁶, CR⁸ and CR⁹ wherein the meaning of R¹⁰, R⁶, R⁸,             and R⁹ is described above; in a further preferred embodiment             Z² is a nitrogen atom and Z¹, Z³, Z⁴ and Z⁵ are respectively             CR¹⁰, CR⁷, CR⁸ and CR⁹ wherein the meaning of R¹⁰, R⁷, R⁸,             and R⁹ is described above;         -   in the moiety of formula (Wc) in a preferred embodiment Z⁶             is an oxygen atom, a sulfur atom, a NR¹⁶ group; preferably             it is a sulfur atom or a NR¹⁶; wherein R¹⁶ is preferably a             C₁-C₄₀-alkyl radical; more preferably Z⁶ is a sulfur atom;             and Z⁷, Z⁸, Z⁹ and Z¹⁰ are respectively a CR¹⁴, CR¹⁵, CR¹⁶             and a carbon atom, wherein R¹⁴ is a hydrogen atom or a             C₁-C₄₀-alkyl radical such as methyl or ethyl; and R¹⁵ and             R¹⁶ are hydrogen atoms or C₁-C₄₀-alkyl radicals.

A further preferred class of compounds of formula (I) has formula (IIa), (IIb), or (IIc):

Wherein M, L, X, R¹, R⁴, R⁶, R⁷, R⁸, R⁹ and R¹⁰ have the meaning reported above and R¹¹ and R¹² equal to or different from each other, are hydrogen atoms or C₁-C₄₀ hydrocarbon radicals optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; preferably R¹¹ and R¹² are hydrogen atoms or linear or branched, cyclic or acyclic, C₁-C₄₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀ alkynyl radicals, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; more preferably R¹¹ and R¹² are hydrogen atoms or C₁-C₁₀-alkyl radicals such as methyl or ethyl radicals. Preferably the metallocene compounds of formula (I) have C₂ symmetry. Metallocene symmetry classes can be found on Resconi et al. Chemical Reviews, 2000, Vol. 100, No. 4 1263 and references herein cited.

Preferably the metallocene compounds to be used in the process of the present invention are in their racemic(rac) or racemic-like form. Racemic(rac) and racemic-like form are described in PCT/EP2005/052688.

Examples of compounds having formula (I) are as follows

-   Me₂Si(6-Me-4-Ph-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂, -   Me₂Si(6,8-Me2-4-Ph-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂, -   Me₂Si[6-Me-4-(4-t-BuPh)-1,2,3,5-tetrahydro-s-indacen-7-yl]₂ZrCl₂, -   Me₂Si(6,8-Me2-4-(4-t-BuPh)-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂, -   Me₂Si[6-Me-4-(2-MePh)-1,2,3,5-tetrahydro-s-indacen-7-yl]₂ZrCl₂, -   Me₂Si(6,8-Me2-4-(2-MePh)-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂, -   Me₂Si(1,1,3,3,6-Me5-4-(2-MePh)-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂, -   Me₂Si[6-Me-4-(2,5-Me₂Ph)-1,2,3,5-tetrahydro-s-indacen-7-yl]₂ZrCl₂, -   Me₂Si[6-Me-4-(4-biphenyl)-1,2,3,5-tetrahydro-s-indacen-7-yl]₂ZrCl₂, -   Me₂Si(1,1,3,3,6-Me5-4-Ph-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂, -   Me₂Si[1,1,3,3,6-Me5-4-(4-tBuPh)-1,2,3,5-tetrahydro-s-indacen-7-yl]₂ZrCl₂, -   Me₂Si(2,2,6-Me3-4-Ph-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂, -   Me₂Si(2-Me-4-Ph-1H-cyclopenta[b]naphthalen-1-yl)₂ZrCl₂, -   Me₂Si(2,5,8-Me3-4-Ph-1H-cyclopenta[b]naphthalen-1-yl)₂ZrCl₂, -   Me₂Si(2-Me-4-Ph-5,6,7,8-tetrahydro-1H-cyclopenta[b]naphthalen-1-yl)₂ZrCl₂, -   Me₂Si(2,6-Me2-4-Ph-5H-1-thia-s-indacen-7-yl)₂ZrCl₂, -   Me₂Si(2,3,6-Me3-4-Ph-5H-1-thia-s-indacen-7-yl)₂ZrCl₂, -   Me₂Si(2,6-Me2-4-(4-t-BuPh)-5H-1-thia-s-indacen-7-yl)₂ZrCl₂, -   Me₂Si(2,3,6-Me3-4-(4-t-BuPh)-5H-1-thia-s-indacen-7-yl)₂ZrCl₂, -   Me₂Si(2-Me-4-Ph-1,5,6,7,8,9-hexahydrocyclohepta[f]     inden-1-yl)₂ZrCl₂, -   Me₂Si(6-Me-4-(2-benzothiophenyl)-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂, -   Me₂Si(6-Me-4-(2-(5-methylthiophenyl))-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂, -   Me₂Si(6-Me-4-(2-(5-methylfuryl))-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂, -   Me₂Si(6-Me-4-(4-pyridyl)-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂, -   C₂H₄(6-Me-4-Ph-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂, -   C₂H₄(6,8-Me2-4-Ph-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂, -   Ph₂Si(6-Me-4-Ph-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂, -   Ph₂Si(6,8-Me2-4-Ph-1,2,3,5-tetrahydro-s-indacen-7-yl)₂ZrCl₂ -   Me₂Si(6-Me-4-(2-(5-methylthiophenyl))-1,2,3,5-tetrahydro-s-indacen-7-yl)     (6-Me-4-Ph-1,2,3,5-tetrahydro-s-indacen-7-yl)ZrCl₂ -   Me₂Si(6,8-Me2-4-Ph-1,2,3,5-tetrahydro-s-indacen-7-yl)     (6-Me-4-(4-t-BuPh)-1,2,3,5-tetrahydro-s-indacen-7-yl) ZrCl₂     -   and their correspondent dimethyl derivatives.

The process of the present invention is preferably carried out at a temperature ranging from 60° C. to 200° C., more preferably at a temperature ranging from 70° C. to 150° C., even more preferably from 80° C. to 120° C.

The alumoxanes used in the process according to the invention are considered to be linear, branched or cyclic compounds containing at least one group of the type:

wherein the substituents U, same or different, are defined above.

In particular, alumoxanes of the formula:

can be used in the case of linear compounds, wherein n¹ is 0 or an integer of from 1 to 40 and the substituents U are defined as above; or alumoxanes of the formula:

can be used in the case of cyclic compounds, wherein n2 is an integer from 2 to 40 and the U substituents are defined as above.

Examples of alumoxanes suitable for use according to the present invention are methylalumoxane (MAO), tetra-(isobutyl)alumoxane (TIBAO), tetra-(2,4,4-trimethyl-pentyl)alumoxane (TIOAO), tetra-(2,3-dimethylbutyl)alumoxane (TDMBAO) and tetra-(2,3,3-trimethylbutyl)alumoxane (TTMBAO).

Particularly interesting cocatalysts are those described in WO 99/21899 and in WO01/21674 in which the alkyl and aryl groups have specific branched patterns.

Non-limiting examples of aluminium compounds that can be reacted with water to give suitable alumoxanes (b), described in WO 99/21899 and WO01/21674, are:

-   tris(2,3,3-trimethyl-butyl)aluminium,     tris(2,3-dimethyl-hexyl)aluminium,     tris(2,3-dimethyl-butyl)aluminium,     tris(2,3-dimethyl-pentyl)aluminium,     tris(2,3-dimethyl-heptyl)aluminium,     tris(2-methyl-3-ethyl-pentyl)aluminium,     tris(2-methyl-3-ethyl-hexyl)aluminium,     tris(2-methyl-3-ethyl-heptyl)aluminium,     tris(2-methyl-3-propyl-hexyl)aluminium,     tris(2-ethyl-3-methyl-butyl)aluminium,     tris(2-ethyl-3-methyl-pentyl)aluminium,     tris(2,3-diethyl-pentyl)aluminium,     tris(2-propyl-3-methyl-butyl)aluminium,     tris(2-isopropyl-3-methyl-butyl)aluminium,     tris(2-isobutyl-3-methyl-pentyl)aluminium,     tris(2,3,3-trimethyl-pentyl)aluminium,     tris(2,3,3-trimethyl-hexyl)aluminium,     tris(2-ethyl-3,3-dimethyl-butyl)aluminium,     tris(2-ethyl-3,3-dimethyl-pentyl)aluminium,     tris(2-isopropyl-3,3-dimethyl-butyl)aluminium,     tris(2-trimethylsilyl-propyl)aluminium,     tris(2-methyl-3-phenyl-butyl)aluminium,     tris(2-ethyl-3-phenyl-butyl)aluminium,     tris(2,3-dimethyl-3-phenyl-butyl)aluminium,     tris(2-phenyl-propyl)aluminium,     tris[2-(4-fluoro-phenyl)-propyl]aluminium,     tris[2-(4-chloro-phenyl)-propyl]aluminium,     tris[2-(3-isopropyl-phenyl)-propyl]aluminium,     tris(2-phenyl-butyl)aluminium,     tris(3-methyl-2-phenyl-butyl)aluminium,     tris(2-phenyl-pentyl)aluminium,     tris[2-(pentafluorophenyl)-propyl]aluminium,     tris[2,2-diphenyl-ethyl]aluminium and     tris[2-phenyl-2-methyl-propyl]aluminium, as well as the     corresponding compounds wherein one of the hydrocarbyl groups is     replaced with a hydrogen atom, and those wherein one or two of the     hydrocarbyl groups are replaced with an isobutyl group.

Amongst the above aluminium compounds, trimethylaluminium (TMA), triisobutylaluminium (TIBA), tris(2,4,4-trimethyl-pentyl)aluminium (TIOA), tris(2,3-dimethylbutyl)aluminium (TDMBA) and tris(2,3,3-trimethylbutyl)aluminium (TTMBA) are preferred.

Non-limiting examples of compounds able to form an alkylmetallocene cation are compounds of formula D⁺E⁻, wherein D⁺ is a Brønsted acid, able to donate a proton and to react irreversibly with a substituent X of the metallocene of formula (I) and E⁻ is a compatible anion, which is able to stabilize the active catalytic species originating from the reaction of the two compounds, and which is sufficiently labile to be removed by an olefinic monomer. Preferably, the anion E⁻ comprises one or more boron atoms. More preferably, the anion E⁻ is an anion of the formula BAr₄ ⁽⁻⁾, wherein the substituents Ar which can be identical or different are aryl radicals such as phenyl, pentafluorophenyl or bis(trifluoromethyl)phenyl. Tetrakis-pentafluorophenyl borate is particularly preferred compound, as described in WO 91/02012. Moreover, compounds of formula BAr₃ can be conveniently used. Compounds of this type are described, for example, in the International patent application WO 92/00333. Other examples of compounds able to form an alkylmetallocene cation are compounds of formula BAr₃P wherein P is a substituted or unsubstituted pyrrol radical. These compounds are described in WO01/62764. Compounds containing boron atoms can be conveniently supported according to the description of DE-A-19962814 and DE-A-19962910. All these compounds containing boron atoms can be used in a molar ratio between boron and the metal of the metallocene comprised between about 1:1 and about 10:1; preferably 1:1 and 2.1; more preferably about 1:1.

Non limiting examples of compounds of formula D⁺E⁻ are:

-   Tributylammonium tetrakis(pentafluorophenyl)aluminate,     Tributylammonium tetrakis(trifluoromethylphenyl)borate,     Tributylammonium tetrakis(4-fluorophenyl)borate,     N,N-Dimethylbenzylammoniumtetrakis(pentafluorophenyl)borate,     N,N-Dimethylhexylamoniumtetrakis(pentafluorophenyl)borate,     N,N-Dimethylaniliniumtetrakis(pentafluorophenyl)borate,     N,N-Dimethylaniliniumtetrakis(pentafluorophenyl)aluminate,     N,N-Dimethylbenzylammoniumtetrakis(pentafluorophenyl)borate,     N,N-Dimethylhexylamoniumtetrakis(pentafluorophenyl)borate,     Di(propyl)ammoniumtetrakis(pentafluorophenyl)borate,     Di(cyclohexyl)ammoniumtetrakis(pentafluorophenyl)borate,     Triphenylcarbeniumtetrakis(pentafluorophenyl)borate,     Triphenylcarbeniumtetrakis(pentafluorophenyl)aluminate,     Ferroceniumtetrakis(pentafluorophenyl)borate,     Ferroceniumtetrakis(pentafluorophenyl)aluminate,     Triphenylcarbeniumtetrakis(pentafluorophenyl)borate, and     N,N-Dimethylaniliniumtetrakis(pentafluorophenyl)borate.

Additional examples of compounds of formula D⁺E⁻ that can be used according to the present invention are described in WO 04/005360, WO 02/102811 and WO 01/62764.

Organic aluminum compounds used as compound c) are those of formula H_(j)AIU_(3-j) or H_(j)Al₂U_(6-j) as described above.

The catalyst system of the present invention can be prepared by contacting the metallocene of formula (I) and a suitable cocatalyst, in a solvent. The cocatalyst is preferably the reaction product of methylalumoxane and triisobutylaluminum.

The catalyst of the present invention can be preferably prepared according to PCT/EP2005/002479 both by distilling off toluene or by following the described procedure but without such a distillation. The catalysts of the present invention can also be supported on an inert carrier. This is achieved by depositing the metallocene compound a) or the product of the reaction thereof with the component b), or the component b) and then the metallocene compound a) on an inert support. The support can be a porous solid such as talc, a sheet silicate, an inorganic oxide or a finely divided polymer powder (e.g. polyolefin). Suitable inorganic oxides may be found among the oxides of elements of groups 2, 3, 4, 5, 13, 14, 15 and 16 of the Periodic Table of the Elements. Examples of oxides preferred as supports include silicon dioxide, aluminum oxide, and also mixed oxides of the elements calcium, aluminum, silicon, magnesium or titanium and also corresponding oxide mixtures, magnesium halides, styrene/divinylbenzene copolymers, polyethylene or polypropylene. Other inorganic oxides which can be used alone or in combination with the above-mentioned preferred oxidic supports are, for example, MgO, ZrO₂, TiO₂ or B₂O₃.

A suitable class of supports which can be used is that constituted by porous organic supports functionalized with groups having active hydrogen atoms. Particularly suitable are those in which the organic support is a partially crosslinked styrene polymer. Supports of this type are described in European application EP-633 272.

Another class of inert supports particularly suitable for use according to the invention is that of polyolefin porous prepolymers, particularly polyethylene.

A further suitable class of inert supports for use according to the invention is that of porous magnesium halides such as those described in International application WO 95/32995.

The support materials used preferably have a specific surface area in the range from 10 to 1 000 m²/g, a pore volume in the range from 0.1 to 5 ml/g and a mean particle size of from 1 to 500 μm. Preference is given to supports having a specific surface area in the range from 50 to 500 m²/g, a pore volume in the range from 0.5 to 3.5 ml/g and a mean particle size in the range from 5 to 350 μm. Particular preference is given to supports having a specific surface area in the range from 200 to 400 m²/g, a pore volume in the range from 0.8 to 3.0 ml/g and a mean particle size of from 10 to 300 μm.

The inorganic support can be subjected to a thermal treatment, e.g. to remove adsorbed water. Such a drying treatment is generally carried out at from 80 to 300° C., preferably from 100 to 200° C., with drying at from 100 to 200° C. preferably being carried out under reduced pressure and/or a blanket of inert gas (e.g. nitrogen), or the inorganic support can be calcined at from 200 to 1000° C. to produce the desired structure of the solid and/or set the desired OH concentration on the surface. The support can also be treated chemically using customary desiccants such as metal alkyls, preferably aluminum alkyls, chlorosilanes or SiCl₄, or else methylaluminoxane. Appropriate treatment methods are described, for example, in WO 00/31090.

The inorganic support material can also be chemically modified. For example, treatment of silica gel with (NH₄)₂SiF₆ leads to fluorination of the silica gel surface, or treatment of silica gels with silanes containing nitrogen-, fluorine- or sulfur-containing groups leads to correspondingly modified silica gel surfaces.

Organic support materials such as finely divided polyolefin powders (e.g. polyethylene, polypropylene or polystyrene) can also be used and are preferably likewise freed of adhering moisture, solvent residues or other impurities by means of appropriate purification and drying operations before use. It is also possible to use functionalized polymer supports, e.g. supports based on polystyrene, via whose functional groups, for example carboxylic or hydroxy groups, at least one of the catalyst components can be immobilized. The solid compound obtained by supporting the catalyst system object of the present invention on a carrier in combination with the further addition of the alkylaluminium compound either as such or prereacted with water if necessary.

In a preferred embodiment the polymerization process of the present invention is carried out in solution.

For the purpose of the present invention the term solution polymerization means that the polymer is fully soluble in the polymerization medium at the polymerization temperature used, and in a concentration range of at least 5% by weight; preferably from 5 to 50% by weight.

In order to have the polymer completely soluble in the polymerization medium, a mixtures of monomers in the presence of an inert solvent can be used. This solvent can be an aliphatic or cycloaliphatic hydrocarbon such as hexane, heptane, isooctane, isododecane, cyclohexane and methylcyclohexane. It is also possible to use mineral spirit or a hydrogenated diesel oil fraction. Also aromatic hydrocarbons can be used such as toluene. Preferred solvents to be used are cyclohexane and methylcyclohexane. The 1-butene or alpha-olefin content in the mixture can be varied according to the final comonomer content wished in the copolymer and the relative reactivity ratio of the comonomers. The ethylene content in the liquid phase of the polymerization medium preferably ranges from 1% to 10% by weight; more preferably from 2% to 8% by weight.

The ratio of the comonomers varies accordingly, depending on the wished final copolymer and the relative comonomers reactivity ratio of the catalyst system.

The skilled man is able to select the ratio of ethylene and comonomer in order to obtain the whished copolymer.

The copolymers obtained according to the process of the present invention, especially those having high comonomer content, are very sticky, this makes it difficult to produce in an industrial plant when the polymerization process is carried out in slurry or in gas phase because of the fouling in the reactor. On the contrary when a solution polymerization process is carried this problem is avoided.

According to the process of the present invention ethylene is contacted with at least an alpha olefin of formula CH₂=CHA wherein T is a C₂-C₂₀ alkyl radical. Examples of alpha olefin of formula CH₂=CHT are 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 4,6-dimethyl-1-heptene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene and 1-eicosene. Preferred comonomer to be used 1-butene, and 1-hexene.

The content of ethylene derived units in the copolymers obtained according to the present invention ranges preferably from 60% by mol to 95% by mol. Preferably the content of ethylene derived units ranges from 75% by mol to 95% by mol.

The molecular weight can be very effectively controlled by the addition of hydrogen.

The molecular weight distribution can be varied by using mixtures of different metallocene compounds or by carrying out the polymerization in several stages which differ as to the polymerization temperature and/or the concentrations of the molecular weight regulators and/or the monomers concentration. Moreover by carrying out the polymerization process by using a combination of two different metallocene compounds a polymer endowed with a broad melting is produced.

The polymer obtained according to the process of the present invention can further contain up to 10% by mol of a non conjugated diene. Non conjugated dienes can be a straight chain, branched chain or cyclic hydrocarbon diene having from 6 to 20 carbon atoms. Examples of suitable non-conjugated dienes are:

-   -   straight chain acyclic dienes, such as 1,4-hexadiene and         1,6-octadiene;     -   branched chain acyclic dienes, such as 5-methyl-1,4-hexadiene,         3,7-dimethyl-1,6-octadiene, 3,7-dimethyl-1,7-octadiene and mixed         isomers of dihydro myricene and dihydroocinene;     -   single ring alicyclic dienes, such as 1,3-cyclopentadiene,         1,4-cyclohexadiene, 1,5-cyclooctadiene and 1,5-cyclododecadiene;     -   multi-ring alicyclic fused and bridged ring dienes, such as         tetrahydroindene, methyl tetrahydroindene, dicyclopentadiene,         bicyclo-(2,2,1)-hepta-2,5-diene; and     -   alkenyl, alkylidene, cycloalkenyl and cycloalkylidene         norbornenes, such as 5-methylene-2-norbornene (MNB),         5-propenyl-2-norbornene, 5-isopropylidene-2-norbornene,         5-(4-cyclopentenyl)-2-norbornene,         5-cyclohexylidene-2-norbornene, 5-vinyl-2-norbornene and         norbornadiene.

Preferred dienes are 1,4-hexadiene (HD), 5-ethylidene-2-norbornene (ENB), 5-vinylidene-2-norbornene (VNB), 5-methylene-2-norbornene (MNB) and dicyclopentadiene (DCPD). Particularly preferred dienes are 5-ethylidene-2-norbornene (ENB) and 1,4-hexadiene (HD).

When present the non-conjugated dienes are preferably incorporated into the polymer in an amount from 0.1% to about 10% by mol, preferably from 0.2% to 5% by mol, and more preferably from 0.3% to 3% by mol. If desired, more than one diene may be incorporated simultaneously, for example HD and ENB, with total diene incorporation within the limits specified above.

Therefore a further object of the present invention is a polymerization process comprising contacting under polymerization conditions ethylene, an alpha olefin of formula CH₂=CHA and a non conjugated diene, in the presence of a catalyst system obtainable by contacting:

-   -   b) at least a metallocene compound of formula (I)

-   -   b) alumoxane or a compound capable of forming an alkyl         metallocene cation; and optionally     -   c) an organo aluminum compound.

Preferably the process is carried out in solution.

The following examples are given to illustrate and not to limit the invention.

EXAMPLES General Characterization

Intrinsic Viscosity (IV) in Tetrahydronaphthalene

The measurement were done in tetrahydronaphthalene (THN) solution obtained by dissolving the polymer at 135° C. for 1 hour.

¹³C-NMR Analysis of Ethylene-Butene Copolymers

The polymer microstructure was investigated by ¹³C-NMR analysis. The samples were dissolved with a 8% wt/v concentration in 1,1,2,2-tetrachloroethane-d₂ at 120° C. The ¹³C-NMR spectra were acquired at 120° C. on a Bruker DPX400 spectrometer operating at 100.61 MHz. Each spectrum was acquired with a 90° pulse, 15 seconds of delay between pulses and CPD (WALTZ 16) to remove ¹H-¹³C coupling. About 1500 transients were stored in 32K data points using a spectral window of 6000 Hz.

The assignments of the peaks were made according to Randall[1] and the triad distribution and copolymer compositions was determined according to the method proposed by Kakugo.[2] (taking into account peak averlapping).

The Tβδ peak at 37.24 ppm (nomenclature according to reference 3) was used as internal reference. The product of reactivity ratios r₁×r₂ was calculated from the triads according to Carman.[3]

-   [1] J. C. Randall, Macromol. Chem. Phys. 1989, C29, 201. -   [2] M. Kakugo, Y. Naito, K. Mizunuma, T. Miyatake, Macromolecules     1982, 15, 1150. -   [3] C. J. Carman, R. A. Harrington, C. E. Wilkes. Macromolecules     1977, 10, 535.     Chemicals and Characterization.

All chemicals were handled using standard Schlenk techniques. Methylalumoxane (MAO) was received from Albemarle as a 30% wt/wt toluene solution and used as such.

Racemic-dimethylsilylbis(2-methyl-4-(4-tert-butyl-phenyl)-inden-1-yl)dichlorozirconium C-1 was prepared according to WO 98/40331 (example 65); racemic-dimethylsilylbis(2-methyl-4-(4-tert-butylphenyl)-1,5,6,7-tetrahydro-s-indacen-1-yl)dichlorozirconium A-1 was prepared according to the procedure described in EP05102189.7.

Catalyst Systems

Preparation of the Catalyst Systems.

Catalyst System S1

900 g of TIBA/cyclohexane solution (332 g/L), 1070 mL of MAO/toluene solution (Albemarle 30% wt/wt, d=0.92 g/mL) and 1600 g of cyclohexane were mixed in a 12 L thermostated autoclave. After 1 h of stirring at 50° C., 9.67 g of A-1 (previously suspended in 60 mL of toluene) were added to the MAO/TIBA solution. The resulting mixture was stirred for additional 90 min at 50° C., then 4400 g of cyclohexane were added and after additional 10 min stirring, the mixture was filtered to finally give a red solution (concentration=76 g_(TOT)/L and 0.97 g_(metallocene)/L).

Catalyst System S2

13.5 mL of TIBA/cyclohexane solution (113 g/L) were mixed with 3.2 mL of MAO/toluene solution (Albemarle 30% wt/wt, d=0.92 g/mL, 15.3 mmol MAO) to obtain a MAO/TIBA molar ratio of 2:1. The solution was stirred for 1 h at room temperature and transferred into a 50 mL Schlenk flask containing C-1 (28.4 mg, 38.3 μmol). The final solution was diluted with 7.7 mL of cyclohexane. Final mixture concentration=100 g_(TOT)/L and 1.165 g_(metallocene)/L; color=dark red solution.

Polymerization Tests.

The amount of monomers (respectively C₁ and C₂) and solvent initially charged into the autoclave, and the ratio of the two monomers constantly fed during the test were calculated via ASPEN ONE simulation, based on the desired composition for the final copolymer and on the reactivity ratio R of a given metallocene:

$R = {\frac{\left( {C_{1}/C_{2}} \right)_{polymer}}{\left( {C_{1}/C_{2}} \right)_{liquidphase}} = \frac{F}{f}}$

Ethylene-1-butene Copolymerization Tests Comparative Example 1

A 4.4 L jacketed stainless-steel autoclave, equipped with a mechanical stirrer and a 50-mL stainless-steel vial, was purified by washing with an Al(1-Bu)₃ solution in hexane and dried at 70° C. in a stream of nitrogen.

11.9 mL of a 100 g/L Al(i-Bu)₃/hexane solution (corresponding to 6 mmol of Al(i-Bu)₃), 1000 g of cyclohexane, 111.5 g of ethylene and 121.6 g of butene were charged into the autoclave, and heated to 100° C., thus producing a liquid composition of 15/85 (wt/wt) monomers/cyclohexane, and a pressure of 22 bar-g.

2 mL of the catalyst system S2 containing the catalyst/cocatalyst mixture (1.165 mg metallocene/mL solution) were diluted with 5 mL of cyclohexane, charged in the stainless-steel vial and injected into the autoclave by nitrogen overpressure.

A constant ethylene/butene mixture 60/40% wt was continuously fed for 30 minutes to maintain the pressure at 22 bar-g for a total consumption of 19 g of ethylene and 12 g of butene.

The autoclave was pressurized with nitrogen up to 30 bar, the bottom discharge valve opened and the polymer discharged into a heated steel tank and treated for 10 min with water steam. The tank heating was switched off and a flow of nitrogen at 0.5 bar-g was fed to remove the water. The steel tank was finally opened, the wet polymer collected, and dried overnight under reduced pressure at 70° C. The results of the analysis performed on the polymer samples are reported in Table 1.

Comparative Example 2

The procedure of comparative example 1 was repeated feeding 1000 g of cyclohexane, 143.7 g of ethylene, and 101 g of butene in order to obtain, at 100° C. and 28 bar-g, a liquid composition of 15/85% wt monomers/cyclohexane.

2.5 mL of the catalyst system S2 containing the catalyst/cocatalyst mixture (1.165 mg metallocene/mL solution) were diluted with 5 mL of cyclohexane, charged in the stainless-steel vial and injected into the autoclave by nitrogen overpressure.

A constant ethylene/butene mixture 70/30% wt was continuously fed for 30 minutes to maintain the pressure of 28 bar-g: 33.4 g of ethylene and 14.2 g of butene were consumed. The results of the analysis performed on the polymer samples are reported in Table 1.

Comparative Example 3

The procedure of comparative example 1 was repeated feeding 1000 g of cyclohexane, 183 g of ethylene, and 75 g of butene in order to obtain, at 100° C. and 32 bar-g, a liquid composition of 15/85% wt monomers/cyclohexane.

3 mL of the catalyst system S2 containing the catalyst/cocatalyst mixture (1.165 mg metallocene/mL solution) were diluted with 5 mL of cyclohexane, charged in the stainless-steel vial and injected into the autoclave by nitrogen overpressure.

A constant ethylene/butene mixture 80/20% wt was continuously fed for 30 minutes to maintain the pressure of 32 bar-g: 110 g of ethylene and 28.4 g of butene were consumed. The results of the analysis performed on the polymer samples are reported in Table 1.

Example 4

The procedure of comparative example 1 was repeated feeding 1000 g of cyclohexane, 170 g of ethylene, and 84 g of butene in order to obtain, at 100° C. and 31 bar-g, a liquid composition of 15/85% wt monomers/cyclohexane.

1 mL of the catalyst system SI containing the catalyst/cocatalyst mixture (0.97 mg metallocene/mL solution) was diluted with 5 mL of cyclohexane, charged in the stainless-steel vial and injected into the autoclave by nitrogen overpressure.

A constant ethylene/butene mixture 80/20% wt was continuously fed for 30 minutes to maintain the pressure of 32 bar-g: 74.9 g of ethylene and 18.5 g of butene were consumed. The results of the analysis performed on the polymer samples are reported in Table 1.

Example 5

The procedure of comparative example 1 was repeated feeding 1000 g of cyclohexane, 55.2 g of ethylene, and 158 g of butene in order to obtain, at 100° C. and 15 bar-g, a liquid composition of 15/85% wt monomers/cyclohexane. 400 normal mL of hydrogen were charged through a stainless-steel cylinder equipped with a pressure gauge and connected to the autoclave.

0.5 mL of the catalyst system S1 containing the catalyst/cocatalyst mixture (0.97 mg metallocene/mL solution) were diluted with 5 mL of cyclohexane, charged in the stainless-steel vial and injected into the autoclave by nitrogen overpressure.

A constant ethylene/butene mixture 60/40% wt was continuously fed for 30 minutes to maintain the pressure of 15 bar-g: 52 g of ethylene and 35 g of butene were consumed. The results of the analysis performed on the polymer samples are reported in Table 1.

Example 6

The procedure of comparative example 1 was repeated feeding 1091 g of cyclohexane, 187 g of ethylene, and 250 g of butene in order to obtain, at 100° C. and 34 bar-g, a liquid composition of 25/75% wt monomers/cyclohexane. 300 normal mL of hydrogen were charged through a stainless-steel cylinder equipped with a pressure gauge and connected to the autoclave. 0.5 mL of the catalyst system SI containing the catalyst/cocatalyst mixture (0.97 mg metallocene/mL solution) were diluted with 5 mL of cyclohexane, charged in the stainless-steel vial and injected into the autoclave by nitrogen overpressure.

A constant ethylene/butene mixture 80/20% wt was continuously fed for 30 minutes to maintain the pressure of 15 bar-g: 47.7 g of ethylene and 11.6 g of butene were consumed. The results of the analysis performed on the polymer samples are reported in Table 1.

Example 7

The procedure of comparative example 1 was repeated feeding 901 g of cyclohexane, 175 g of ethylene, and 405 g of butene in order to obtain, at 100° C. and 33 bar-g, a liquid composition of 36/64% wt monomers/cyclohexane. 300 normal mL of hydrogen were charged in the autoclave.

0.5 mL of the catalyst system SI containing the catalyst/cocatalyst mixture (0.97 mg metallocene/mL solution) were diluted with 5 mL of cyclohexane, charged in the stainless-steel vial and injected into the autoclave by nitrogen overpressure.

A constant ethylene/butene mixture 70/30% wt was continuously fed for 30 minutes to maintain the pressure of 33 bar-g: 17.7 g of ethylene and 7.6 g of butene were consumed. The results of the analysis performed on the polymer samples are reported in Table 1.

Example 8

The procedure of comparative example 1 was repeated feeding 664 g of cyclohexane, 163 g of ethylene, and 585 g of butene in order to obtain, at 100° C. and 34 bar-g, a liquid composition of 50/50% wt monomers/cyclohexane. 300 normal mL of hydrogen were charged in the autoclave.

1 mL of the catalyst system SI containing the catalyst/cocatalyst mixture (0.97 mg metallocene/mL solution) was diluted with 5 mL of cyclohexane, charged in the stainless-steel vial and injected into the autoclave by nitrogen overpressure.

A constant ethylene/butene mixture 60/40% wt was continuously fed for 30 minutes to maintain the pressure of 34 bar-g: 39 g of ethylene and 26.4 g of butene were consumed. The results of the analysis performed on the polymer samples are reported in Table 1.

TABLE l Catalyst H₂ Yield kg_(POL)/ I.V. Ethylene from Ethylene from Example System (mL) (g) (g_(met)*30′) (dL/g, THN) NMR (% wt) NMR (% mol) 1* S2 0 10 4.4 2.00 73.6 84.8 2* S2 0 27 9.4 2.43 81.1 89.6 3* S2 0 24 6.9 2.47 88.6 94.0 4 S1 0 106 109 4.90 89.6 94.5 5 S1 400 100 205 0.84 61.5 76.1 6 S1 300 74 153 3.53 83.3 90.9 7 S1 300 38 78 2.51 73.0 84.4 8 S1 300 65 67 2.22 64.1 78.1 *comparative examples 

The invention claimed is:
 1. A polymerization process comprising contacting under polymerization conditions ethylene and at least one alpha olefin of formula CH2=CHA, wherein A is a C₂-C₂₀ alkyl radical, to obtain a copolymer comprising from 95% by mol to 75% by mol of ethylene derived units in presence of a catalyst system obtained by contacting: a) at least a metallocene compound of formula (I)

and b) alumoxane or a compound capable of forming an alkyl metallocene cation; wherein: M is an atom of a transition metal selected from group 3, 4, or the lanthanide or actinide groups in the Periodic Table of Elements; X equal to or different from each other, is hydrogen, halogen, R, OR, OR′O, OSO₂CF₃, OCOR, SR, NR₂ or PR₂; R is a linear or branched, cyclic or acyclic, C₁-C₄₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀ alkynyl, C₆-C₄₀-aryl, C₇-C₄₀-alkylaryl or C₇-C₄₀-arylalkyl radical, optionally comprising at least one heteroatom belonging to groups 13-17 of the Periodic Table of Elements; R′ is a C₁-C₂₀-alkylidene, C₆-C₂₀-arylidene, C₇-C₂₀-alkylarylidene, or C₇-C₂₀-arylalkylidene radical; L is a divalent bridging group selected from C₁-C₂₀ alkylidene, C₃-C₂₀ cycloalkylidene, C₆-C₂₀ arylidene, C₇-C₂₀ alkylarylidene, or C₇-C₂₀ arylalkylidene radicals, optionally comprising at least one heteroatom belonging to groups 13-17 of the Periodic Table of Elements, or a silylidene radical comprising up to 5 silicon atoms; R¹ is a linear C₁-C₄₀ hydrocarbon radical optionally comprising at least one heteroatom belonging to groups 13-17 of the Periodic Table of Elements; R₂ and R₃ are part of 4-7 membered ring condensed to the benzene ring of the indenyl moiety, the ring optionally comprising at least one heteroatom belonging to groups 13-16 of the Periodic Table of Elements, wherein the valence of each atom forming the ring being filled with R¹⁸ radicals; R¹⁸ equal to or different from each other, are hydrogen or C₁-C₄₀ hydrocarbon radicals; R⁴ is hydrogen; W is an aromatic 5 or 6 membered ring optionally comprising at least one heteroatom belonging to groups 13-16 of the Periodic Table of Elements, wherein the valence of each atom of the ring is substituted with hydrogen or is optionally substituted with at least one R⁵ group; and R⁵ equal to or different from each other, are C₁-C₄₀ hydrocarbon radicals optionally comprising at least one heteroatom belonging to groups 13-17 of the Periodic Table of Elements.
 2. The process according to claim 1, wherein R¹ is methyl, ethyl, an alpha branched aryl, or an arylalkyl radical comprising from 2 to 20 carbon atoms optionally comprising at least one O, N, S, P or Se atom.
 3. The process according to claim 1, wherein the catalyst system further comprises c) an organo aluminum compound.
 4. The process according to claim 1, wherein M is zirconium, titanium or hafnium; X is hydrogen, halogen, OR′O or R group; L is Si(R¹¹)₂; R¹¹ is a linear or branched, cyclic or acyclic, C₁-C₄₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀ alkynyl, C₆-C₄₀-aryl, C₇-C₄₀-alkylaryl or C₇-C₄₀-arylalkyl radical; and R¹ is a C₁-C₁₀-alkyl radical.
 5. The process according to claim 1, wherein R² and R³ are part of 5-6 membered ring condensed to the benzene ring of the indenyl moiety, the ring being substituted with R¹⁸ radicals; wherein R¹⁸ is hydrogen or a linear or branched, C₁-C₂₀-alkyl radical.
 6. The process according to claim 1, wherein W is selected from the group consisting of the following moieties of formula (Wa), (Wb) and (Wc):

wherein the * represents the point in which the moiety is bound to the indenyl moiety of the compound of formula (I); R⁶, R⁷, R⁸, R⁹ and R¹⁰, equal to or different from each other, are hydrogen or C₁-C₄₀ hydrocarbon radicals optionally comprising at least one heteroatom belonging to groups 13-17 of the Periodic Table of Elements; Z¹ is nitrogen or a CR¹⁰ group; Z² is nitrogen or a CR⁶ group; Z³ is nitrogen or a CR⁷ group; Z⁴ is nitrogen or a CR⁸ group; Z⁵ is nitrogen or a CR⁹ group, with the proviso that not more than 2 groups among Z¹, Z², Z³, Z⁴ and Z⁵ are nitrogen atoms; Z⁶ is oxygen, sulfur, a NR¹³ group or a CR¹³ group; Z⁷ is oxygen, sulfur, a NR¹⁴ group or a CR¹⁴ group; Z⁸ is oxygen, sulfur, a NR¹⁵ group or a CR¹⁵ group; Z⁹ is oxygen, sulfur, a NR¹⁶ group or a CR¹⁶ group; ¹⁰ is nitrogen or carbon, with the proviso that not more than 1 group among Z⁶, Z⁷, Z⁸, Z⁹ or Z¹⁰ is sulfur, oxygen, or a nitrogen-containing group selected from nitrogen, NR¹³, NR¹⁴, NR¹⁵, and NR¹⁶; and R¹³, R¹⁴, R¹⁵ and R¹⁶, equal to or different from each other, are hydrogen or C₁-C₄₀ hydrocarbon radicals optionally comprising at least one heteroatom belonging to groups 13-17 of the Periodic Table of Elements.
 7. The process according to claim 1, wherein the compound of formula (I) comprises formula (IIa), (IIb) or (IIc):

wherein M is an atom of a transition metal selected from group 3, 4, or the lanthanide or actinide groups in the Periodic Table of Elements; X equal to or different from each other, is hydrogen, halogen, R, OR, OR′O, OSO₂CF₃, OCOR, SR, NR₂ or PR₂; R is a linear or branched, cyclic or acyclic, C₁-C₄₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀ alkynyl, C₆-C₄₀-aryl, C₇-C₄₀-alkylaryl or C₇-C₄₀-arylalkyl radical, optionally comprising at least one heteroatom belonging to groups 13-17 of the Periodic Table of Elements; R′ is a C₁-C₂₀-alkylidene, C₆-C₂₀-arylidene, C₇-C₂₀-alkylarylidene, or C₇-C₂₀-arylalkylidene radical; L is a divalent bridging group selected from C₁-C₂₀ alkylidene, C₃-C₂₀ cycloalkylidene, C₆-C₂₀ arylidene, C₇-C₂₀ alkylarylidene, or C₇-C₂₀) arylalkylidene radicals, optionally comprising at least one heteroatom belonging to groups 13-17 of the Periodic Table of Elements, or a silylidene radical comprising up to 5 silicon atoms; R¹ is a linear C₁-C₄₀ hydrocarbon radical optionally comprising at least one heteroatom belonging to groups 13-17 of the Periodic Table of Elements; R⁴ is hydrogen; R⁵ is a C₁-C₄₀ hydrocarbon radical optionally comprising at least one heteroatom belonging to groups 13-17 of the Periodic Table of Elements R⁶, R⁷, R⁸, R⁹ and R¹⁰, equal to or different from each other, are hydrogen or C₁-C₄₀ hydrocarbon radicals optionally comprising at least one heteroatom belonging to groups 13-17 of the Periodic Table of Elements; R¹⁴, R¹⁵ and R¹⁶, equal to or different from each other, are hydrogen or C₁-C₄₀ hydrocarbon radicals optionally comprising at least one heteroatom belonging to groups 13-17 of the Periodic Table of Elements; and R¹¹ and R¹² equal to or different from each other, are hydrogen atoms or C₁-C₄₀ hydrocarbon radicals optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements.
 8. The process according to claim 1, wherein the process is carried out at a temperature ranging from 60° C. to 200° C.
 9. The process according to claim 1, wherein the process further comprises a polymerization medium comprising a mixture of liquid monomers, optionally in presence of an aliphatic or cycloaliphatic hydrocarbon solvent.
 10. The process according to claim 1, wherein the alpha olefins of formula CH2=CHA are 1-butene or 1-hexene.
 11. The process according to claim 1, wherein the copolymer further comprises up to 20% by mol of a non-conjugated diene. 